Solid state imaging device, method of manufacturing the same, and imaging apparatus

ABSTRACT

A solid state imaging device including: a plurality of sensor sections formed in a semiconductor substrate in order to convert incident light into an electric signal; a peripheral circuit section formed in the semiconductor substrate so as to be positioned beside the sensor sections; and a layer having negative fixed electric charges that is formed on a light incidence side of the sensor sections in order to form a hole accumulation layer on light receiving surfaces of the sensor sections.

RELATED APPLICATION DATA

This application is a continuation of U.S. patent application Ser. No.12/237,671, filed Sep. 25, 2008, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentapplication claims the benefit of priority to Japanese PatentApplication No. 2007-259501 filed in the Japanese Patent Office on Oct.3, 2007, the entirety of which is incorporated by reference herein tothe extent permitted by law.

BACKGROUND OF THE INVENTION

The present invention relates to a solid state imaging device having ahole accumulated diode, a method of manufacturing the same, and animaging apparatus.

Solid state imaging devices, such as a CCD (charge coupled device) and aCMOS image sensor, are widely used in a video camera, a digital stillcamera, and the like. Improvement in sensitivity and noise reduction areimportant issues in all kinds of solid state imaging devices.

In particular, a dark current, which is detected as a very small currentwhen an electric charge (electron) generated from a minute defect in asubstrate interface of a light receiving surface is input as a signal,or a dark current generated due to the interface state on the interfacebetween a sensor section and an upper layer even though there is no puresignal charge generated by photoelectric conversion of incident light ina state where there is no incident light is a noise to be reduced in thesolid state imaging device.

As a technique of suppressing generation of a dark current caused by theinterface state, for example, an embed type photodiode structure havinga hole accumulation layer 23 formed of a P⁺ layer on a sensor section(for example, a photodiode) 12 is used as shown in FIG. 9B. Moreover, inthis specification, the embed type photodiode structure is referred toas an HAD (hole accumulated diode) structure. As shown in FIG. 9A, in astructure where the HAD structure is not provided, electrons generateddue to the interface state flow to the photodiode as a dark current. Onthe other hand, as shown in FIG. 9B, in the HAD structure, generation ofelectrons from the interface is suppressed by the hole accumulationlayer 23 formed on the interface. In addition, even if electric charges(electrons) are generated from the interface, the electric charges(electrons) do not flow to a charge accumulation section, which is apotential well in an N⁺ layer of the sensor section 12, but flow to thehole accumulation layer 23 of the P⁺ layer in which many holes exist.Accordingly, the electric charges (electrons) can be eliminated. As aresult, since it can be prevented that the electric charges generateddue to the interface are detected as a dark current, the dark currentcaused by the interface state can be suppressed.

A method of suppressing the dark current maybe adopted in both a CCD anda CMOS image sensor and may also be adopted to not only a knowntop-emission-type image sensor but also a back illuminated image sensor(for example, refer to JP-A-2003-338615).

As a method of forming the HAD structure, it is common to perform ionimplantation of impurities for forming the P⁺ layer, for example, boron(B) or boron difluoride (BF₂) through a thermally oxidized silicon layeror a CVD oxide silicon layer formed on a substrate, to activate injectedimpurities by annealing, and then to form a p-type region near theinterface. However, heat treatment in a high temperature of 700° C. ormore is essential in order to activate doped impurities. Accordingly,formation of the hole accumulation layer using ion implantation isdifficult in a low-temperature process at 400° C. or less. Also in thecase of desiring to avoid long-time activation at high temperature inorder to suppress diffusion of dopant, the method of forming a holeaccumulation layer in which ion implantation and annealing are performedis not preferable.

Furthermore, when a silicon oxide or a silicon nitride formed on anupper layer of the sensor section is formed in a low-temperature plasmaCVD method, for example, the interface state is reduced compared with aninterface between of a light receiving surface and a layer formed athigh temperature. The reduction in interface state increases a darkcurrent.

As described above, in the case of desiring to avoid ion implantationand annealing process at high temperature, not only the holeaccumulation layer cannot be formed by known ion implantation but also adark current is further increased. In order to solve the problem, itbecomes necessary to form a hole accumulation layer in another methodthat is not based on ion implantation in the related art.

As an example, there is a method of forming a layer having negativefixed electric charges on an upper layer of a sensor section. In thismethod, a hole accumulation layer is formed on the interface at a sideof the light receiving surface of the sensor section by the electricfield caused by the layer having negative fixed electric charges.Accordingly, electric charges (electrons) generated from the interfaceis suppressed. In addition, even if electric charges (electrons) aregenerated from the interface, the electric charges (electrons) do notflow to a charge accumulation portion which is a potential well in thesensor section but flow to the hole accumulation layer in which manyholes exist. As a result, the electric charges (electrons) can beeliminated. Thus, since it can be prevented that a dark currentgenerated by the electric charges on the interface is detected in thesensor section, a dark current caused by the interface state issuppressed. Thus, by using the layer having negative fixed electriccharges, the HAD structure can be formed without ion implantation andannealing. The layer having negative fixed electric charges may beformed of a hafnium oxide (HfO₂) layer, for example.

However, as described above, when the configuration in which the layerhaving negative fixed electric charges is formed on the light receivingsurface is applied to a back illuminated CCD or CMOS image sensor, forexample, a layer 22 having negative fixed electric charges is formed onthe entire light receiving surface 12 s of a sensor section 12 as shownin FIG. 10. Accordingly, a hole accumulation layer 23 (P⁺ layer) isformed not only in a pixel region where the HAD needs to be formed butalso on a surface of a semiconductor substrate 11 on a peripheralcircuit section 14.

For example, when a well region, a diffusion layer, a circuit, and thelike (a diffusion layer 15 is shown as an example in the drawing) arepresent in the peripheral circuit section 14 so that a negative electricpotential is generated on a back side of the semiconductor substrate 11,holes having positive electric charges are drawn to the negativeelectric potential to be diffused. Accordingly, a desired negativeelectric potential is not obtained due to the positive electric chargesdrawn but an electric potential biased toward a positive side from adesigned value is output. As a result, an applied voltage of the sensorsection using the electric potential is adversely affected, causing aproblem that a pixel characteristic changes.

SUMMARY OF THE INVENTION

The problem to be solved is that since a desired negative electricpotential is not obtained and an electric potential biased toward apositive electric potential side from a designed value is output in aperipheral circuit section, an applied voltage of a sensor section usingthe electric potential is adversely affected, causing a pixelcharacteristic to change.

In view of the above, it is desirable to allow a peripheral circuitsection to normally operate by eliminating the influence of a layerhaving negative fixed electric charges in the peripheral circuitsection.

According to a first embodiment of the present invention, a solid stateimaging device includes: a plurality of sensor sections formed in asemiconductor substrate in order to convert incident light into anelectric signal; a peripheral circuit section formed in thesemiconductor substrate so as to be positioned beside the sensorsections; and a layer having negative fixed electric charges that isformed on the semiconductor substrate at a light incidence side of thesensor sections in order to form a hole accumulation layer on lightreceiving surfaces of the sensor sections. An N-type impurity region isformed between the peripheral circuit section and the layer havingnegative fixed electric charges.

In the solid state imaging device according to the first embodiment ofthe present invention, since the N-type impurity region is formedbetween the peripheral circuit section and the layer having negativefixed electric charges, the movement of holes generated on the interfaceof the semiconductor substrate is prevented by the N-type impurityregion. Accordingly, since it is prevented that the holes move into theperipheral circuit section, a change in an electric potential of a wellregion, a diffusion layer, a circuit, and the like that are formed inthe peripheral circuit section so as to generate a negative electricpotential is suppressed.

According to a second embodiment of the present invention, a solid stateimaging device includes: a plurality of sensor sections formed in asemiconductor substrate in order to convert incident light into anelectric signal; a peripheral circuit section formed in thesemiconductor substrate so as to be positioned beside the sensorsections; and a layer having negative fixed electric charges that isformed on a light incidence side of the sensor sections in order to forma hole accumulation layer on light receiving surfaces of the sensorsections.

In the solid state imaging device according to the second embodiment ofthe present invention, since the layer having negative fixed electriccharges that forms the hole accumulation layer on the light receivingsurfaces of the sensor sections is formed on the light incidence side ofthe sensor sections, the layer having negative fixed electric charges isnot formed in the peripheral circuit section. Accordingly, holes do notgather in the peripheral circuit section because the hole accumulationlayer generated by the layer having negative fixed electric charges isnot formed in the peripheral circuit section, and a change in anelectric potential of a well region, a diffusion layer, a circuit, andthe like that are formed in the peripheral circuit section to generatethe negative electric potential does not occur because the holes do notmove into the peripheral circuit section.

According to a third embodiment of the present invention, a method ofmanufacturing a solid state imaging device having a plurality of sensorsections formed in a semiconductor substrate in order to convertincident light into an electric signal, a peripheral circuit sectionformed in the semiconductor substrate so as to be positioned beside thesensor sections, and a layer having negative fixed electric charges thatis formed on a light incidence side of the sensor sections in order toform a hole accumulation layer on light receiving surfaces of the sensorsections includes the step of: forming an N-type impurity region betweenthe peripheral circuit section and the layer having negative fixedelectric charges.

In the solid state imaging device according to the third embodiment ofthe present invention, since the N-type impurity region is formedbetween the peripheral circuit section and the layer having negativefixed electric charges, the movement of holes generated on the interfaceof the semiconductor substrate is prevented by the N-type impurityregion. Accordingly, since it is prevented that the holes move into theperipheral circuit section, a change in an electric potential of a wellregion, a diffusion layer, a circuit, and the like that are formed inthe peripheral circuit section so as to generate a negative electricpotential is suppressed.

According to a fourth embodiment of the present invention, a method ofmanufacturing a solid state imaging device having a plurality of sensorsections formed in a semiconductor substrate in order to convertincident light into an electric signal, a peripheral circuit sectionformed in the semiconductor substrate so as to be positioned beside thesensor sections, and a layer having negative fixed electric charges thatis formed on a light incidence side of the sensor sections in order toform a hole accumulation layer on light receiving surfaces of the sensorsections includes the steps of : forming the layer having negative fixedelectric charges; and removing the layer having negative fixed electriccharges on the peripheral circuit section.

In the method according to the fourth embodiment of the presentinvention, since the layer having negative fixed electric charges thatforms the hole accumulation layer on the light receiving surfaces of thesensor sections is formed on the light incidence side of the sensorsections, the layer having negative fixed electric charges is not formedin the peripheral circuit section. Accordingly, holes do not gather inthe peripheral circuit section because the hole accumulation layergenerated by the layer having negative fixed electric charges is notformed in the peripheral circuit section, and a change in an electricpotential of a well region, a diffusion layer, a circuit, and the likethat are formed in the peripheral circuit section to generate thenegative electric potential does not occur because the holes do not moveinto the peripheral circuit section.

According to a fifth embodiment of the present invention, an imagingapparatus includes: a condensing optical section that condenses incidentlight; a solid state imaging device that receives the light condensed inthe condensing optical section and performs photoelectric conversion ofthe received light; and a signal processing section that processes asignal photoelectrically converted. The solid state imaging deviceincludes: a plurality of sensor sections formed in a semiconductorsubstrate in order to convert incident light into an electric signal; aperipheral circuit section formed in the semiconductor substrate so asto be positioned beside the sensor sections; and a layer having negativefixed electric charges that is formed on the semiconductor substrate ata light incidence side of the sensor sections in order to form a holeaccumulation layer on light receiving surfaces of the sensor sections.An N-type impurity region is formed between the peripheral circuitsection and the layer having negative fixed electric charges.

In the imaging apparatus according to the fifth embodiment of thepresent invention, the solid state imaging device according to theembodiment of the present invention is used. Therefore, even if thelayer having negative fixed electric charges that forms the holeaccumulation layer on the light receiving surfaces of the sensorsections is formed, the solid state imaging device capable ofsuppressing a change in an electric potential of a well region, adiffusion layer, a circuit, and the like that are formed in theperipheral circuit section to generate the negative electric potentialis used.

According to a sixth embodiment of the present invention, an imagingapparatus includes: a condensing optical section that condenses incidentlight; a solid state imaging device that receives the light condensed inthe condensing optical section and performs photoelectric conversion ofthe received light; and a signal processing section that processes asignal photoelectrically converted. The solid state imaging deviceincludes: a plurality of sensor sections formed in a semiconductorsubstrate in order to convert incident light into an electric signal; aperipheral circuit section formed in the semiconductor substrate so asto be positioned beside the sensor sections; and a layer having negativefixed electric charges that is formed on a light incidence side of thesensor sections in order to form a hole accumulation layer on lightreceiving surfaces of the sensor sections.

In the imaging apparatus according to the sixth embodiment of thepresent invention, the solid state imaging device according to theembodiment of the present invention is used. Therefore, even if thelayer having negative fixed electric charges that forms the holeaccumulation layer on the light receiving surfaces of the sensorsections is formed, the solid state imaging device in which a change inan electric potential of a well region, a diffusion layer, a circuit,and the like, which are formed in the peripheral circuit section togenerate the negative electric potential, is used.

In the solid state imaging device according to the first embodiment ofthe present invention, the N-type impurity region is formed between acircuit of the peripheral circuit section and the layer having negativefixed electric charges. Accordingly, since it can be prevented thatholes generated on the interface of the semiconductor substrate moveinto the peripheral circuit section, there is an advantage that a changein an electric potential of the circuit formed in the peripheral circuitsection can be suppressed. As a result, a dark current of the sensorsection can be reduced by the hole accumulation layer generated by thelayer having negative fixed electric charges formed on the lightreceiving surface of the sensor section without fluctuating the electricpotential of the peripheral circuit section.

In the solid state imaging device according to the second embodiment ofthe present invention, the layer having negative fixed electric chargesis not formed in the peripheral circuit section. Accordingly, since itcan be prevented that holes are generated on the interface of thesemiconductor substrate of the peripheral circuit section, there is anadvantage that a change in an electric potential of a circuit formed inthe peripheral circuit section does not occur. As a result, a darkcurrent of the sensor section can be reduced by the hole accumulationlayer generated by the layer having negative fixed electric chargesformed on the light receiving surface of the sensor section withoutfluctuating the electric potential of the peripheral circuit section.

In the method of manufacturing a solid state imaging device according tothe third embodiment of the present invention, the N-type impurityregion is formed between a circuit of the peripheral circuit section andthe layer having negative fixed electric charges. Accordingly, since itcan be prevented that holes generated on the interface of thesemiconductor substrate move into the peripheral circuit section, thereis an advantage that a change in an electric potential of the circuitformed in the peripheral circuit section can be suppressed. As a result,a dark current of the sensor section can be reduced by the holeaccumulation layer generated by the layer having negative fixed electriccharges formed on the light receiving surface of the sensor sectionwithout fluctuating the electric potential of the peripheral circuitsection.

In the method of manufacturing a solid state imaging device according tothe fourth embodiment of the present invention, the layer havingnegative fixed electric charges is not formed in the peripheral circuitsection. Accordingly, since it can be prevented that holes are generatedon the interface of the semiconductor substrate of the peripheralcircuit section, there is an advantage that a change in an electricpotential of a circuit formed in the peripheral circuit section does notoccur. As a result, a dark current of the sensor section can be reducedby the hole accumulation layer generated by the layer having negativefixed electric charges formed on the light receiving surface of thesensor section without fluctuating the electric potential of theperipheral circuit section.

In the imaging apparatuses according to the fifth and sixth embodimentsof the present invention, the solid state imaging device according tothe embodiment of the present invention capable of reducing a darkcurrent of the sensor section without fluctuating the electric potentialof the peripheral circuit section is used as an imaging device.Accordingly, there is an advantage that a high-quality image can berecorded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating the schematicconfiguration of a solid state imaging device according to an embodiment(first example) of the present invention;

FIG. 2 is a cross-sectional view illustrating the schematicconfiguration of a solid state imaging device according to an embodiment(second example) of the present invention;

FIGS. 3A to 3C are cross-sectional views illustrating a manufacturingprocess in a method of manufacturing a solid state imaging deviceaccording to an embodiment (first example) of the present invention;

FIG. 4 is a cross-sectional view illustrating a manufacturing process inthe method of manufacturing a solid state imaging device according tothe embodiment (first example) of the present invention;

FIGS. 5A and 5B are cross-sectional views illustrating a manufacturingprocess in a modification of the manufacturing method according to thefirst example;

FIGS. 6A to 6C are cross-sectional views illustrating a manufacturingprocess in the method of manufacturing a solid state imaging deviceaccording to the embodiment (second example) of the present invention;

FIGS. 7A and 7B are cross-sectional views illustrating a manufacturingprocess in the method of manufacturing a solid state imaging deviceaccording to the embodiment (second example) of the present invention;

FIG. 8 is a block diagram illustrating an imaging apparatus according toan embodiment of the present invention;

FIGS. 9A and 9B are cross-sectional views illustrating the schematicconfiguration of a light receiving section, which shows a technique ofsuppressing generation of a dark current due to the interface state; and

FIG. 10 is a cross-sectional view illustrating the schematicconfiguration of a known solid state imaging device, in which a layerhaving negative fixed electric charges is formed, in order to explainproblems of the known solid state imaging device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A solid state imaging device according to an embodiment (first example)of the present invention will be described with reference to across-sectional view of FIG. 1 illustrating the schematic configuration.

As shown in FIG. 1, a solid state imaging device 1 includes a sensorsection 12, which performs photoelectric conversion of incident light,in a semiconductor substrate (or a semiconductor layer) 11. On a sidesection of the sensor section 12, a peripheral circuit section 14 inwhich a well region, a diffusion layer, a circuit, and the like (adiffusion layer 15 is shown as an example in the drawing) are formedwith a pixel separating region 13 interposed therebetween is provided.The following explanation will be made using the semiconductor substrate11. On a light receiving surface 12 s of the sensor section (including ahole accumulation layer 23 which will be described later) 12, aninterface state lowering layer 21 is formed. The interface statelowering layer 21 is formed of a silicon oxide (SiO₂) layer, forexample. On the interface state lowering layer 21, a layer 22 havingnegative fixed electric charges is formed. Thus, the hole accumulationlayer 23 is formed at a side of the light receiving surface 12 s of thesensor section 12. Accordingly, at least on the sensor section 12, theinterface state lowering layer 21 is formed in a film thickness that thehole accumulation layer 23 is formed at a side of the light receivingsurface 12 s of the sensor section 12 by the layer 22 having negativefixed electric charges. For example, the film thickness is set to beequal to or larger than one atomic layer and equal to or smaller than100 nm.

In the case when the solid state imaging device 1 is a CMOS imagesensor, for example, a pixel circuit configured to include transistors,such as a transfer transistor, a reset transistor, an amplifyingtransistor, and a selection transistor, is provided as the peripheralcircuit section 14. In addition, a driving circuit which performs anoperation of reading a signal on a read line of a pixel array sectionformed by the plurality of sensor sections 12, a vertical scanningcircuit which transmits the read signal, a shift register or an addressdecoder, a horizontal scanning circuit, and the like are included.

Moreover, in the case when the solid state imaging device 1 is a CCDimage sensor, for example, a read gate which reads a signal chargephotoelectrically converted by the sensor section to a vertical transfergate and a vertical charge transfer section which transmits the readsignal charge in the vertical direction are provided as the peripheralcircuit section 14. In addition, a horizontal charge transfer sectionand the like are included.

Furthermore, on a side of the semiconductor substrate 11 opposite alight incidence side thereof, a wiring layer 53 configured to includewiring lines 51, which are provided over a plurality of layers, and aninsulating layer 52 for insulation between layers of the wiring lines 51and between the wiring lines 51 of each layer is formed.

The layer 22 having negative fixed electric charges is formed of ahafnium oxide (HfO₂) layer, an aluminium oxide (Al₂O₃) layer, azirconium oxide (ZrO₂) layer, a tantalum oxide (Ta₂O₅) layer, or atitanium oxide (TiO₂) layer, for example. Such kinds of layers have beenused as a gate insulating layer of an insulated gate field effecttransistor and the like. Accordingly, since a layer forming method isknown, the layers can be easily formed. Examples of the layer formingmethod include a chemical vapor deposition method, a sputtering method,and an atomic layer deposition method. Here, it is preferable to use theatomic layer deposition method because an SiO₂ layer which lowers theinterface state can be simultaneously formed in a thickness of 1 nmduring the film formation. In addition, as materials other than thosedescribed above, a lanthanum oxide (La₂O₃), a praseodymium oxide(Pr₂O₃), a cerium oxide (CeO₂), a neodymium oxide (Nd₂O₃), a promethiumoxide (Pm₂O₃), a samarium oxide (Sm₂O₃), an europium oxide (Eu₂O₃), agadolinium oxide (Gd₂O₃), a terbium oxide (Tb₂O₃), a dysprosium oxide(Dy₂O₃), a holmium oxide (Ho₂O₃), an erbium oxide (Er₂O₃), a thuliumoxide (Tm₂O₃), an ytterbium oxide (Yb₂O₃), a lutetium oxide (Lu₂O₃), anyttrium oxide (Y₂O₃), and the like maybe mentioned. In addition, thelayer 22 having negative fixed electric charges may also be formed of ahafnium nitride layer, an aluminum nitride layer, a hafnium oxynitridelayer, or an aluminum oxynitride layer.

The layer 22 having negative fixed electric charges may have silicone(Si) or nitrogen (N) added in a range in which an insulation property isnot adversely affected. The concentration is appropriately determined ina range in which an insulation property of the layer is not adverselyaffected. Thus, it becomes possible to raise the thermal resistance ofthe layer or an ability to prevent implantation of ions during a processby adding the silicon (Si) or the nitrogen (N).

An N-type impurity region 16 is formed in the semiconductor substrate 11between the peripheral circuit section 14 and the layer 22 havingnegative fixed electric charges. The N-type impurity region 16 is formedby N-type impurities, such as phosphorus (P) and arsenic (As), forexample, and is formed by using ion implantation, for example. TheN-type impurity region has an impurity profile equivalent to a channelstop, for example.

An insulating layer 41 is formed on the layer 22 having negative fixedelectric charges, and a light shielding layer 42 is formed on theinsulating layer 41 positioned above the peripheral circuit section 14.Although not shown, a region where light is not incident on the sensorsection 12 is generated by the light shielding layer 42, and a blacklevel in an image is determined by an output of the sensor section 12.In addition, since the light shielding layer 42 prevents light frombeing incident on the peripheral circuit section 14, a characteristicchange caused by light incident on the peripheral circuit section issuppressed. Moreover, an insulating layer 43 which allows the incidentlight to be transmitted therethrough is formed. It is preferable that asurface of the insulating layer 43 be flat. Furthermore, ananti-reflection layer (not shown), a color filter layer 44 and acondensing lens 45 are formed on the insulating layer 43.

In the solid state imaging device 1 according to the first embodiment,since the N-type impurity region 16 is formed between the peripheralcircuit section 14 and the layer 22 having negative fixed electriccharges, the movement of holes generated on the interface of thesemiconductor substrate 11 is prevented by the N-type impurity region16. Accordingly, since it is prevented that the holes move into theperipheral circuit section 14, a change in an electric potential of awell region, the diffusion layer 15, a circuit, and the like that areformed in the peripheral circuit section 14 to generate the negativeelectric potential is suppressed. As a result, a dark current of thesensor section 12 can be reduced by the hole accumulation layer 23generated by the layer 22 having negative fixed electric charges formedon the light receiving surface 12 s of the sensor section 12 withoutfluctuating the electric potential of the peripheral circuit section 14.

Next, a solid state imaging device according to an embodiment (secondexample) of the present invention will be described with reference to across-sectional view of FIG. 2 illustrating the schematic configuration.

As shown in FIG. 2, a solid state imaging device 2 includes a sensorsection 12, which performs photoelectric conversion of incident light,in a semiconductor substrate (or a semiconductor layer) 11. On a sidesection of the sensor section 12, a peripheral circuit section 14 inwhich a well region, a diffusion layer, a circuit, and the like (adiffusion layer 15 is shown as an example in the drawing) are formedwith a pixel separating region 13 interposed therebetween is provided.The following explanation will be made using the semiconductor substrate11. On a light receiving surface 12 s of the sensor section (includingthe hole accumulation layer 23 which will be described later) 12, theinterface state lowering layer 21 is formed. The interface statelowering layer 21 is formed of a silicon oxide (SiO₂) layer, forexample. On the interface state lowering layer 21, a layer 22 havingnegative fixed electric charges is formed. Thus, the hole accumulationlayer 23 is formed at a side of the light receiving surface 12 s of thesensor section 12. Accordingly, at least on the sensor section 12, theinterface state lowering layer 21 is formed in a film thickness that thehole accumulation layer 23 is formed at a side of the light receivingsurface 12 s of the sensor section 12 by the layer 22 having negativefixed electric charges. For example, the film thickness is set to beequal to or larger than one atomic layer and equal to or smaller than100 nm.

In the case when the solid state imaging device 1 is a CMOS imagesensor, for example, a pixel circuit configured to include transistors,such as a transfer transistor, a reset transistor, an amplifyingtransistor, and a selection transistor, is provided as the peripheralcircuit section 14. In addition, a driving circuit which performs anoperation of reading a signal on a read line of a pixel array sectionformed by the plurality of sensor sections 12, a vertical scanningcircuit which transmits the read signal, a shift register or an addressdecoder, a horizontal scanning circuit, and the like are included.

Moreover, in the case when the solid state imaging device 1 is a CCDimage sensor, for example, a read gate which reads a signal chargephotoelectrically converted by the sensor section to a vertical transfergate and a vertical charge transfer section which transmits the readsignal charge in the vertical direction are provided as the peripheralcircuit section 14. In addition, a horizontal charge transfer sectionand the like are included.

Furthermore, on a side of the semiconductor substrate 11 opposite alight incidence side thereof, a wiring layer 53 configured to includewiring lines 51, which are provided over a plurality of layers, and aninsulating layer 52 for insulation between layers of the wiring lines 51and between the wiring lines 51 of each layer is formed.

The layer 22 having negative fixed electric charges is formed of ahafnium oxide (HfO₂) layer, an aluminium oxide (Al₂O₃) layer, azirconium oxide (ZrO₂) layer, a tantalum oxide (Ta₂O₅) layer, or atitanium oxide (TiO₂) layer, for example. Such kinds of layers have beenused as a gate insulating layer of an insulated gate field effecttransistor and the like. Accordingly, since a layer forming method isknown, the layers can be easily formed. Examples of the layer formingmethod include a chemical vapor deposition method, a sputtering method,and an atomic layer deposition method. Here, it is preferable to use theatomic layer deposition method because an SiO₂ layer which lowers theinterface state can be simultaneously formed in a thickness of 1 nmduring the film formation. In addition, as materials other than thosedescribed above, a lanthanum oxide (La₂O₃), a praseodymium oxide(Pr₂O₃), a cerium oxide (CeO₂), a neodymium oxide (Nd₂O₃), a promethiumoxide (Pm₂O₃), a samarium oxide (Sm₂O₃), an europium oxide (Eu₂O₃), agadolinium oxide (Gd₂O₃), a terbium oxide (Tb₂O₃), a dysprosium oxide(Dy₂O₃), a holmium oxide (Ho₂O₃), an erbium oxide (Er₂O₃), a thuliumoxide (Tm₂O₃), an ytterbium oxide (Yb₂O₃), a lutetium oxide (Lu₂O₃), anyttrium oxide (Y₂O₃), and the like may be mentioned. In addition, thelayer 22 having negative fixed electric charges may also be formed of ahafnium nitride layer, an aluminum nitride layer, a hafnium oxynitridelayer, or an aluminum oxynitride layer.

The layer 22 having negative fixed electric charges may have silicone(Si) or nitrogen (N) added in a range in which an insulation property isnot adversely affected. The concentration is appropriately determined ina range in which an insulation property of the layer is not adverselyaffected. Thus, it becomes possible to raise the thermal resistance ofthe layer or an ability to prevent implantation of ions during a processby adding the silicon (Si) or the nitrogen (N).

The layer 22 having negative fixed electric charges is formed only onthe sensor section 12 so that the hole accumulation layer 23 is formedon the light receiving surface 12 s of the sensor section 12, but is notformed on the peripheral circuit section 14 (light incidence side).

An insulating layer 41 is formed on the layer 22 having negative fixedelectric charges, and a light shielding layer 42 is formed on theinsulating layer 41 positioned above the peripheral circuit section 14.Although not shown, a region where light is not incident on the sensorsection 12 is generated by the light shielding layer 42, and a blacklevel in an image is determined by an output of the sensor section 12.In addition, since the light shielding layer 42 prevents light frombeing incident on the peripheral circuit section 14, a characteristicchange caused by light incident on the peripheral circuit section issuppressed. Moreover, an insulating layer 43 which allows the incidentlight to be transmitted therethrough is formed. It is preferable that asurface of the insulating layer 43 be flat. Furthermore, ananti-reflection layer (not shown) , a color filter layer 44 and acondensing lens 45 are formed on the insulating layer 43.

In the solid state imaging device 2 in the second example, since thelayer 22 having negative fixed electric charges which forms the holeaccumulation layer 23 is formed on the light receiving surface 12 s ofthe sensor section 12, the layer 22 having negative fixed electriccharges is not formed in the peripheral circuit section 14. Accordingly,holes do not gather in the peripheral circuit section 14 because thehole accumulation layer 23 generated by the layer 22 having negativefixed electric charges is not formed in the peripheral circuit section14, and a change in an electric potential of a well region, thediffusion layer 15, a circuit, and the like that are formed in theperipheral circuit section 14 to generate a negative electric potentialdoes not occur because the holes do not move into the peripheral circuitsection 14. As a result, a dark current of the sensor section 12 can bereduced by the hole accumulation layer 23 generated by the layer 22having negative fixed electric charges formed on the light receivingsurface 12 s of the sensor section 12 without fluctuating the electricpotential of the peripheral circuit section 14.

In addition, in the first and second examples, the neighborhood of theinterface can be used as the hole accumulation layer 23 by the negativefixed electric charges present in the layer from immediately afterforming the layer 22 having negative fixed electric charges.Accordingly, a dark current generated by the interface state on theinterface between the sensor section 12 and the interface state loweringlayer 21 is suppressed. That is, electric charges (electrons) generatedfrom the interface is suppressed. In addition, even if electric charges(electrons) are generated from the interface, the electric charges(electrons) do not flow to a charge accumulation portion which is apotential well in the sensor section 12 but flow to the holeaccumulation layer 23 in which many holes exist and accordingly, theelectric charges (electrons) can be removed. Thus, since it can beprevented that a dark current generated by the electric charges on theinterface is detected in the sensor section 12, a dark current caused bythe interface state is suppressed. Furthermore, generation of electronsdue to the interface state is further suppressed since the interfacestate lowering layer 21 is formed on the light receiving surface 12 s ofthe sensor section 12. As a result, it is suppressed that electronsgenerated due to the interface state flow to the sensor section 12 as adark current.

In each of the above examples, a back illuminated solid state imagingdevice that includes a plurality of pixel sections each having thesensor section 12, which serves to convert incident light into anelectric signal, and the wiring layer 53 provided on a surface of thesemiconductor substrate 11 formed with the pixel sections and thatreceives light, which is incident from a side opposite a surface onwhich the wiring layer 53 is formed, in the sensor section 12 has beenexplained. The configuration in the embodiment of the present inventionmay also be applied to a top-emission-type solid state imaging device inwhich incident light is incident on the sensor section from the sidewhere the wiring layer and the like are formed.

Next, a method of manufacturing a solid state imaging device accordingto an embodiment (first example) of the present invention will bedescribed with reference to cross-sectional views of a manufacturingprocess of FIGS. 3A to 4 illustrating main parts. In FIGS. 3A to 4, amanufacturing process of the solid state imaging device 1 is shown as anexample.

As shown in FIG. 3A, the sensor section 12 which performs photoelectricconversion of incident light, the pixel separating region 13 forseparating the sensor section 12, and the peripheral circuit section 14in which a well region, a diffusion layer, a circuit, and the like (thediffusion layer 15 is shown as an example in the drawing) are formedwith the pixel separating region 13 interposed between the peripheralcircuit section 14 and the sensor section 12 are formed in thesemiconductor substrate (or semiconductor layer) 11. Then, on a side ofthe semiconductor substrate 11 opposite the light incidence side, thewiring layer 53 configured to include the wiring lines 51 provided overa plurality of layers and the insulating layer 52 for insulation betweenlayers of the wiring lines 51 and between the wiring lines 51 of eachlayer is formed. A known manufacturing method is used as themanufacturing method configured as described above.

Then, the interface state lowering layer 21 is formed on the lightreceiving surface 12 s of the sensor section 12, actually, on thesemiconductor substrate 11. The interface state lowering layer 21 isformed of a silicon oxide (SiO₂) layer, for example. Subsequently, thelayer 22 having negative fixed electric charges is formed on theinterface state lowering layer 21. Thus, the hole accumulation layer 23is formed at the light receiving surface side of the sensor section 12.Accordingly, at least on the sensor section 12, the interface statelowering layer 21 needs to be formed in a film thickness that the holeaccumulation layer 23 is formed at a side of the light receiving surface12 s of the sensor section 12 by the layer 22 having negative fixedelectric charges. For example, the film thickness is set to be equal toor larger than one atomic layer and equal to or smaller than 100 nm.

The layer 22 having negative fixed electric charges is formed of ahafnium oxide (HfO₂) layer, an aluminium oxide (Al₂O₃) layer, azirconium oxide (ZrO₂) layer, a tantalum oxide (Ta₂O₅) layer, or atitanium oxide (TiO₂) layer, for example. Such kinds of layers have beenused as a gate insulating layer of an insulated gate field effecttransistor and the like. Accordingly, since a layer forming method isknown, the layers can be easily formed. For example, a chemical vapordeposition method, a sputtering method, and an atomic layer depositionmethod may be used as the layer forming method. Here, it is preferableto use the atomic layer deposition method because an SiO₂ layer whichlowers the interface state can be simultaneously formed in a thicknessof 1 nm during the film formation.

In addition, as materials other than those described above, a lanthanumoxide (La₂O₃), a praseodymium oxide (Pr₂O₃), a cerium oxide (CeO₂), aneodymium oxide (Nd₂O₃), a promethium oxide (Pm₂O₃), a samarium oxide(Sm₂O₃), an europium oxide (Eu₂O₃), a gadolinium oxide (Gd₂O₃), aterbium oxide (Tb₂O₃), a dysprosium oxide (Dy₂O₃), a holmium oxide(Ho₂O₃), an erbium oxide (Er₂O₃), a thulium oxide (Tm₂O₃), an ytterbiumoxide (Yb₂O₃), a lutetium oxide (Lu₂O₃), an yttrium oxide (Y₂O₃), andthe like may be used. In addition, the layer 22 having negative fixedelectric charges may also be formed of a hafnium nitride layer, analuminum nitride layer, a hafnium oxynitride layer, or an aluminumoxynitride layer. These layers may also be formed by using the chemicalvapor deposition method, the sputtering method, or the atomic layerdeposition method, for example.

In addition, the layer 22 having negative fixed electric charges mayhave silicon (Si) or nitrogen (N) added in a range in which aninsulation property is not adversely affected. The concentration isappropriately determined in a range in which an insulation property ofthe layer is not adversely affected. Thus, it becomes possible to raisethe thermal resistance of the layer or an ability to preventimplantation of ions during a process by adding the silicon (Si) or thenitrogen (N).

Then, as shown in FIG. 3B, the N-type impurity region is formed byinjecting N-type impurities into the semiconductor substrate 11 betweenthe peripheral circuit section 14 and the layer 22 having negative fixedelectric charges. As a specific example of a method of manufacturing theN-type impurity region 16, a resist layer 61 is formed on the layer 22having negative fixed electric charges and then an opening 62 is formedin the resist layer 61 on the peripheral circuit section 14 by using alithography technique. Thereafter, the N-type impurity region 16 isformed in the semiconductor substrate 11 between the peripheral circuitsection 14 and the layer 22 having negative fixed electric charges byperforming ion implantation of N-type impurities into the semiconductorsubstrate 11 on the peripheral circuit section 14 by using the resistlayer 61 as a mask for ion implantation.

Since the N-type impurity region 16 has the same impurity profile as achannel stop, for example, the N-type impurity region 16 prevents holesgenerated on the interface of the semiconductor substrate 11 from movinginto the semiconductor substrate 11, suppressing a change in an electricpotential of a well region (not shown) or an electric potential of thediffusion layer 15 which is formed in the semiconductor substrate 11.Then, the resist layer 61 is removed.

Then, as shown in FIG. 3C, the insulating layer 41 is formed on thelayer 22 having negative fixed electric charges, and then the lightshielding layer 42 is formed on the insulating layer 41. The insulatinglayer 41 is formed of a silicon oxide layer, for example. In addition,the light shielding layer 42 is formed of a metallic layer having alight shielding property, for example. Thus, reaction of metal of thelight shielding layer 42 and the layer 22 having negative fixed electriccharges formed of an hafnium oxide layer, for example, can be preventedby forming the light shielding layer 42 on the layer 22 having negativefixed electric charges with the insulating layer 41 interposedtherebetween. In addition, since the insulating layer 42 serves as anetching stopper when the light shielding layer is etched, etching damageto the layer 22 having negative fixed electric charges can be prevented.

Although not shown, a region where light is not incident on the sensorsection 12 is generated by the light shielding layer 42, and a blacklevel in an image is determined by an output of the sensor section 12.In addition, since the light shielding layer 42 prevents light frombeing incident on the peripheral circuit section 14, a characteristicchange caused by light incident on the peripheral circuit section issuppressed.

Then, as shown in FIG. 4, the insulating layer 43 for reducing a leveldifference caused by the light shielding layer 42 is formed on theinsulating layer 41. A surface of the insulating layer 43 is preferablyflat and is formed of a coating insulating layer, for example.

Then, an anti-reflection layer (not shown) and the color filter layer 44are formed on the insulating layer 43 positioned above the sensorsection 12 and then the condensing lens 45 is formed on the color filterlayer 44 by a known manufacturing technique. In this case, alight-transmissive insulating layer (not shown) maybe formed between thecolor filter layer 44 and the condensing lens 45 in order to preventmachining damage to the color filter layer 44 at the time of lensprocessing. Thus, the solid state imaging device 1 is formed.

In the first example of the method (first manufacturing method) ofmanufacturing a solid state imaging device, since the N-type impurityregion 16 is formed between the peripheral circuit section 14 and thelayer 22 having negative fixed electric charges, the movement of holesgenerated on the interface of the semiconductor substrate 11 isprevented by the N-type impurity region 16. Accordingly, since it isprevented that the holes move into the peripheral circuit section 14, achange in an electric potential of a well region, the diffusion layer15, a circuit, and the like that are formed in the peripheral circuitsection 14 is suppressed. As a result, a desired negative electricpotential can be obtained in the peripheral circuit section 14.

As a result, a dark current of the sensor section 12 can be reduced bythe hole accumulation layer 23 generated by the layer 22 having negativefixed electric charges formed on the light receiving surface 12 s of thesensor section 12 without fluctuating the electric potential of theperipheral circuit section 14. That is, since the hole accumulationlayer 23 is formed, electric charges (electrons) generated from theinterface is suppressed. Even if electric charges (electrons) aregenerated from the interface, the electric charges (electrons) do notflow to a charge accumulation portion which is a potential well in thesensor section 12 but flow to the hole accumulation layer 23 in whichmany holes exist. As a result, the electric charges (electrons) can beremoved. Thus, since it can be prevented that a dark current generatedby the electric charges on the interface is detected in the sensorsection, a dark current caused by the interface state is suppressed.Furthermore, generation of electrons due to the interface state isfurther suppressed since the interface state lowering layer 21 is formedon the light receiving surface of the sensor section 12. As a result, itis suppressed that electrons generated due to the interface state flowto the sensor section 12 as a dark current.

The N-type impurity region 16 may be formed before the layer 22 havingnegative fixed electric charges is formed or maybe formed after thelayer 22 having negative fixed electric charges is formed as describedabove.

For example, as shown in FIG. 5A, before the interface state loweringlayer 21 (not shown) is formed, a mask for ion implantation is formed onthe semiconductor substrate 11 by using a resist layer 63 having anopening 64 provided on the peripheral circuit section 14 in the samemanner as described above, and then the N-type impurity region 16 isformed in the semiconductor substrate 11 on the peripheral circuitsection 14 by using an ion implantation method. Then, although notshown, the interface state lowering layer 21 and the layer 22 havingnegative fixed electric charges are sequentially formed after removingthe resist layer 63.

In this case, ion implantation damage may occur in the semiconductorsubstrate 11 because ions are implanted into the semiconductor substrate11. However, since a portion of the semiconductor substrate 11 where theN-type impurity region 16 is formed is a region where a well region, adiffusion layer, and the like are not formed, there is no actual damageeven if the ion implantation damage occurs.

Alternatively, for example, as shown in FIG. 5B, after the interfacestate lowering layer 21 is formed, a mask for ion implantation is formedby using a resist layer 65 having an opening 66 provided on theperipheral circuit section 14 in the same manner as described above, andthen the N-type impurity region 16 is formed in the semiconductorsubstrate 11 on the peripheral circuit section 14 by using the ionimplantation method. Then, although not shown, the layer 22 havingnegative fixed electric charges is formed on the interface statelowering layer 21 after removing the resist layer 65.

In this case, since the interface state lowering layer 21 serves as abuffer layer at the time of ion implantation, the ion implantationdamage to the semiconductor substrate 11 is reduced.

Thus, the N-type impurity region 16 may also be formed before formingthe layer 22 having negative fixed electric charges.

Next, a method of manufacturing a solid state imaging device accordingto an embodiment (second example) of the present invention will bedescribed with reference to cross-sectional views of a manufacturingprocess of FIGS. 6A to 7B illustrating main parts. In FIGS. 6A to 7B, amanufacturing process of the solid state imaging device 2 is shown as anexample.

As shown in FIG. 6A, the sensor section 12 which performs photoelectricconversion of incident light, the pixel separating region 13 forseparating the sensor section 12, and the peripheral circuit section 14in which a well region, a diffusion layer, a circuit, and the like (thediffusion layer 15 is shown as an example in the drawing) are formedwith the pixel separating region 13 interposed between the peripheralcircuit section 14 and the sensor section 12 are formed in thesemiconductor substrate (or semiconductor layer) 11. Then, on a side ofthe semiconductor substrate 11 opposite the light incidence side, thewiring layer 53 configured to include the wiring lines 51 provided overa plurality of layers and the insulating layer 52 for insulation betweenlayers of the wiring lines 51 and between the wiring lines 51 of eachlayer is formed. A known manufacturing method is used as themanufacturing method configured as described above.

Then, the interface state lowering layer 21 is formed on the lightreceiving surface 12 s of the sensor section 12, actually, on thesemiconductor substrate 11. The interface state lowering layer 21 isformed of a silicon oxide (SiO₂) layer, for example. Subsequently, thelayer 22 having negative fixed electric charges is formed on theinterface state lowering layer 21. Thus, the hole accumulation layer 23is formed at a side of the light receiving surface 12 s of the sensorsection 12. Accordingly, at least on the sensor section 12, theinterface state lowering layer 21 needs to be formed in a film thicknessthat the hole accumulation layer 23 is formed at a side of the lightreceiving surface 12 s of the sensor section 12 by the layer 22 havingnegative fixed electric charges. For example, the film thickness is setto be equal to or larger than one atomic layer and equal to or smallerthan 100 nm.

The layer 22 having negative fixed electric charges is formed of ahafnium oxide (HfO₂) layer, an aluminium oxide (Al₂O₃) layer, azirconium oxide (ZrO₂) layer, a tantalum oxide (Ta₂O₅) layer, or atitanium oxide (TiO₂) layer, for example. Such kinds of layers have beenused as a gate insulating layer of an insulated gate field effecttransistor and the like. Accordingly, since a layer forming method isknown, the layers can be easily formed. For example, a chemical vapordeposition method, a sputtering method, and an atomic layer depositionmethod may be used as the layer forming method. Here, it is preferableto use the atomic layer deposition method because an SiO₂ layer whichlowers the interface state can be simultaneously formed in a thicknessof 1 nm during the film formation.

In addition, as materials other than those described above, a lanthanumoxide (La₂O₃), a praseodymium oxide (Pr₂O₃), a cerium oxide (CeO₂), aneodymium oxide (Nd₂O₃), a promethium oxide (Pm₂O₃), a samarium oxide(Sm₂O₃), an europium oxide (Eu₂O₃), a gadolinium oxide (Gd₂O₃), aterbium oxide (Tb₂O₃), a dysprosium oxide (Dy₂O₃), a holmium oxide(Ho₂O₃), an erbium oxide (Er₂O₃), a thulium oxide (Tm₂O₃), an ytterbiumoxide (Yb₂O₃), a lutetium oxide (Lu₂O₃), an yttrium oxide (Y₂O₃), andthe like may be used. In addition, the layer 22 having negative fixedelectric charges may also be formed of a hafnium nitride layer, analuminum nitride layer, a hafnium oxynitride layer, or an aluminumoxynitride layer. These layers may also be formed by using the chemicalvapor deposition method, the sputtering method, or the atomic layerdeposition method, for example.

In addition, the layer 22 having negative fixed electric charges mayhave silicon (Si) or nitrogen (N) added in a range in which aninsulation property is not adversely affected. The concentration isappropriately determined in a range in which an insulation property ofthe layer is not adversely affected. Thus, it becomes possible to raisethe thermal resistance of the layer or an ability to preventimplantation of ions during a process by adding the silicon (Si) or thenitrogen (N).

Then, as shown in FIG. 6B, a resist layer 67 is formed on the layer 22having negative fixed electric charges, and then the resist layer 67 onthe peripheral circuit section 14 is removed by using a lithographytechnique.

Then, as shown in FIG. 6C, the layer 22 having negative fixed electriccharges on the peripheral circuit section 14 is removed by using theresist layer 67 (refer to FIG. 6B), as an etching mask.

In case of using dry etching in removing the layer 22 having negativefixed electric charges, a resist layer for dry etching is used as theresist layer 67. In addition, for dry etching, for example, argon andsulfur hexafluoride (SF₆) are used as etching gas. In the case of thelayer 22 having negative fixed electric charges, etching using the aboveetching gas is possible. In addition, etching gas for etching othermetal oxides may also be used to perform the dry etching. Then, theresist layer 67 is removed.

In the above dry etching, the semiconductor substrate 11 is not directlystruck by ions since the interface state lowering layer 21 of a siliconoxide layer is formed on a base of the layer 22 having negative fixedelectric charges. Accordingly, etching damage to the semiconductorsubstrate 11 is reduced.

In case of using wet etching in removing the layer 22 having negativefixed electric charges, a resist layer for wet etching is used as theresist layer 67. In addition, for wet etching, for example, fluoric acidand ammonium fluoride are used as etching solution. In the case of thelayer 22 having negative fixed electric charges, etching using the aboveetching solution is possible. In addition, etching solution for etchingother metal oxides may also be used to perform the well etching. Then,the resist layer 67 is removed.

In the above wet etching, permeation of the etching solution from aperipheral section to a pixel region is suppressed since the interfacestate lowering layer 21 of a silicon oxide layer is formed on a base ofthe layer 22 having negative fixed electric charges.

Then, as shown in FIG. 7A, the insulating layer 41 is formed on thelayer 22 having negative fixed electric charges, and then the lightshielding layer 42 is formed on the insulating layer 41. The insulatinglayer 41 is formed of a silicon oxide layer, for example. In addition,the light shielding layer 42 is formed of a metallic layer having alight shielding property, for example. Thus, reaction of metal of thelight shielding layer 42 and the layer 22 having negative fixed electriccharges formed of an hafnium oxide layer, for example, can be preventedby forming the light shielding layer 42 on the layer 22 having negativefixed electric charges with the insulating layer 41 interposedtherebetween. In addition, since the insulating layer 42 serves as anetching stopper when the light shielding layer is etched, etching damageto the layer 22 having negative fixed electric charges can be prevented.

Although not shown, a region where light is not incident on the sensorsection 12 is generated by the light shielding layer 42, and a blacklevel in an image is determined by an output of the sensor section 12.In addition, since the light shielding layer 42 prevents light frombeing incident on the peripheral circuit section 14, a characteristicchange caused by light incident on the peripheral circuit section issuppressed.

Then, as shown in FIG. 7B, the insulating layer 43 for reducing a leveldifference caused by the light shielding layer 42 is formed on theinsulating layer 41. A surface of the insulating layer 43 is preferablyflat and is formed of a coating insulating layer, for example.

Then, an anti-reflection layer (not shown) and the color filter layer 44are formed on the insulating layer 43 positioned above the sensorsection 12 and then the condensing lens 45 is formed on the color filterlayer 44 by a known manufacturing technique. In this case, alight-transmissive insulating layer (not shown) maybe formed between thecolor filter layer 44 and the condensing lens 45 in order to preventmachining damage to the color filter layer 44 at the time of lensprocessing. Thus, the solid state imaging device 2 is formed.

In the second example of the method of manufacturing a solid stateimaging device, the layer 22 having negative fixed electric charges isnot formed on the peripheral circuit section 14 since the layer 22having negative fixed electric charges on the peripheral circuit section14 is removed. Accordingly, holes do not gather in the peripheralcircuit section 14 because the hole accumulation layer 23 generated bythe layer 22 having negative fixed electric charges is not formed in theperipheral circuit section 14, and a change in an electric potential ofa well region, the diffusion layer 15, a circuit, and the like that areformed in the peripheral circuit section 14 to generate a negativeelectric potential does not occur because the holes do not move into theperipheral circuit section 14.

As a result, a dark current of the sensor section 12 can be reduced bythe hole accumulation layer 23 generated by the layer 22 having negativefixed electric charges formed on the light receiving surface 12 s of thesensor section 12 without fluctuating the electric potential of theperipheral circuit section 14. That is, since the hole accumulationlayer 23 is formed, electric charges (electrons) generated from theinterface is suppressed. Even if electric charges (electrons) aregenerated from the interface, the electric charges (electrons) do notflow to a charge accumulation portion which is a potential well in thesensor section 12 but flow to the hole accumulation layer 23 in whichmany holes exist. As a result, the electric charges (electrons) can beremoved. Thus, since it can be prevented that a dark current generatedby the electric charges on the interface is detected in the sensorsection, a dark current caused by the interface state is suppressed.Furthermore, generation of electrons due to the interface state isfurther suppressed since the interface state lowering layer 21 is formedon the light receiving surface of the sensor section 12. As a result, itis suppressed that electrons generated due to the interface state flowto the sensor section 12 as a dark current.

Each of the solid state imaging devices 1 and 2 in the above examplesincludes a plurality of pixel sections each having a light receivingsection, which converts incident light into an electric signal, and awiring layer provided on a surface of the semiconductor substrate formedwith the pixel sections, and maybe applied to aback illuminated solidstate imaging device having a configuration in which light incident froma side opposite a surface on which the wiring layer is formed isreceived in each of the light receiving sections. It is needless to saythat each of the solid state imaging devices 1 and 2 may also be appliedas a top-emission-type solid state imaging device in which a wiringlayer is formed on a light receiving surface side and incident lightincident on the light receiving section is not blocked by setting anoptical path of the incident light incident on the light receivingsection as a region where the wiring layer is not formed.

Next, an imaging apparatus according to an embodiment (example) of thepresent invention will be described with reference to a block diagram ofFIG. 8. Examples of the imaging apparatus include a video camera, adigital still camera, and a camera of a mobile phone.

As shown in FIG. 8, an imaging apparatus 100 includes a solid stateimaging device (not shown) provided in an imaging section 101. Animaging optical system 102 which images an image is provided at thecondensing side of the imaging section 101. To the imaging section 101,a signal processing section 103 having a driving circuit for driving theimaging section 101, a signal processing circuit which processes animage photoelectrically converted in the solid state imaging device intoan image, and the like are connected. In addition, the image signalprocessed by the signal processing section may be stored in an imagestorage section (not shown). In the imaging apparatus 100, the solidstate imaging devices 1 to 2 described in the above embodiments may beused as the solid state imaging device.

In the imaging apparatus 100 according to the embodiment of the presentinvention, the solid state imaging device 1 or 2 according to theembodiment of the present invention capable of reducing a dark currentof the sensor section without changing the electric potential of theperipheral circuit section, which is advantageous in that a high-qualityimage can be recorded.

Furthermore, the imaging apparatus 100 according to the embodiment ofthe present invention is not limited to having the above-describedconfiguration but may be applied to an imaging apparatus having any kindof configuration as long as it is an imaging apparatus using a solidstate imaging device.

In addition, the solid state imaging device 1 or 2 may be formed as aone chip type device or a module type device in which an imaging sectionand a signal processing section or an optical system are collectivelypackaged and which has an imaging function. In addition, the presentinvention may be applied to not only a solid-state imaging device butalso an imaging apparatus. In this case, an effect of improving imagequality can be obtained in the imaging apparatus. Here, the imagingapparatus refers to a camera or a portable apparatus having an imagingfunction, for example. In addition, the ‘imaging’ includes not onlyimaging of an image at the time of normal photographing of a camera butalso detection of a fingerprint and the like in a broad sense ofmeaning.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A solid state imaging device comprising: a semiconductor substrate; asensor section in the semiconductor substrate and capable of convertingincident light into an electric signal; and a layer having negativefixed electric charges that is formed on a light incidence side of thesensor section in order to form a hole accumulation layer on lightreceiving surface of the sensor section.
 2. The solid state imagingdevice according to claim 1, wherein the layer is a hafnium oxide (HfO2)layer, an aluminium oxide (Al2O3) layer, a zirconium oxide (ZrO2) layer,a tantalum oxide (Ta2O5) layer, or a titanium oxide (TiO2) layer.
 3. Thesolid state imaging device according to claim 1, further comprising: apixel section having the sensor section that converts incident lightinto an electric signal; and a wiring layer provided on a surface of thesemiconductor substrate formed with the pixel section, wherein, thesolid state imaging device is a back illuminated solid state imagingdevice that receives light, which is incident from a side opposite thesurface on which the wiring layer is formed, in the sensor section. 4.The solid state imaging device according to claim 1, wherein: the layerhaving negative fixed electric charges is formed on the light receivingsurface of the sensor section on the semiconductor substrate positionedat the light incidence side of the sensor section, and an N-typeimpurity region is formed between the peripheral circuit section and thelayer having negative fixed electric charges.
 5. The solid state imagingdevice according to claim 4, further comprising: a plurality of pixelsections each a sensor section that converts incident light into anelectric signal; and a wiring layer provided on a surface of thesemiconductor substrate formed with the pixel sections, wherein, thesolid state imaging device is a back illuminated solid state imagingdevice that receives light, which is incident from a side opposite thesurface on which the wiring layer is formed, in the sensor sections. 6.A method of manufacturing a solid state imaging device having a sensorsection formed in a semiconductor substrate in order to convert incidentlight into an electric signal, the method comprising the step of:forming the layer having negative fixed electric charges that is formedon a light incidence side of the sensor sections in order to form a holeaccumulation layer on light receiving surfaces of the sensor sections.7. The solid state imaging device according to claim 6, wherein thelayer is a hafnium oxide (HfO2) layer, an aluminium oxide (Al2O3) layer,a zirconium oxide (ZrO2) layer, a tantalum oxide (Ta2O5) layer, or atitanium oxide (TiO2) layer.
 8. A method of manufacturing a solid stateimaging device having a sensor section formed in a semiconductorsubstrate in order to convert incident light into an electric signal, aperipheral circuit section formed in the semiconductor substrate so asto be positioned beside the sensor sections, and a layer having negativefixed electric charges that is formed on a light incidence side of thesensor sections in order to form a hole accumulation layer on lightreceiving surfaces of the sensor sections, the method comprising thesteps of: forming the layer having negative fixed electric charges; andremoving the layer having negative fixed electric charges on theperipheral circuit section.
 9. The solid state imaging device accordingto claim 8, wherein the layer is a hafnium oxide (HfO2) layer, analuminium oxide (Al2O3) layer, a zirconium oxide (ZrO2) layer, atantalum oxide (Ta2O5) layer, or a titanium oxide (TiO2) layer.
 10. Animaging apparatus comprising: a condensing optical section thatcondenses incident light; a solid state imaging device that receives thelight condensed in the condensing optical section and performsphotoelectric conversion of the received light; and a signal processingsection that processes a signal photoelectrically converted, wherein,the solid state imaging device includes (a) a sensor section formed in asemiconductor substrate in order to convert incident light into anelectric signal; and (b) a layer having negative fixed electric chargesthat is formed on a light incidence side of the sensor section in orderto form a hole accumulation layer on light receiving surface of thesensor section.
 11. The solid state imaging device according to claim10, wherein the layer is a hafnium oxide (HfO2) layer, an aluminiumoxide (Al2O3) layer, a zirconium oxide (ZrO2) layer, a tantalum oxide(Ta2O5) layer, or a titanium oxide (TiO2) layer.
 12. The solid stateimaging device according to claim 10, wherein: the layer having negativefixed electric charges is formed on the light receiving surfaces of thesensor sections on the semiconductor substrate positioned at the lightincidence side of the sensor section, and an the layer having negativefixed electric charges.